Church groups and the family of a Dutch missionary who was killed in July submitted a petition to the Dutch parliament this week to call for an independent investigation into the incident.

The petition has been signed by 600 individuals, 23 organizations and six alliances.

Theo Droog, chairman of the Dutch-Philippines Solidarity movement, said they decided to ask for help from the Dutch government because the task force formed by Philippine authorities to look into the killing of William Geertman "is notÂ seriously proceeding with the case."

The petitioners are asking the Dutch government to pressure Philippine authorities to carry out an independent probe.

Geertman was the second European missionary killed in the Philippines in the past two years. The first victim was Italian missionary Fausto Tentorio who was killed in Mindanao last year.

Geertman had lived in the Philippines since the 1970s and helped organize poor communities to assert their rights to their land. He was executive director of Alay Bayan, a relief and rehabilitation organization.

Alexander Pechtold, acting chairman of the Permanent Commission for Foreign Affairs of the Second Chamber of the Dutch Parliament, noted that Geertman was the 17th environmental activist killed during the administration of President Benigno Aquino. He said the petition will be discussed with the Minister of Foreign Affairs, Frans Timmermans.

Authorities have already filed a murder case against still unnamed suspects, but despite clear photographs of the killers "there is no development in the case after four months," according to Aurora Santiago, Geertman's partner and a member of Alay Bayan.